A product's demand per period follows a normal distribution with mean of 60 and standard deviation of 10. The lead time is 3 periods. What order-up-to level should be used to achieve at least a 90% in-stock probability? (use the normal distribution table posted on Canvas and round up to the nearest integer).

TABLE 14.1 The Distribution Function, F(z), and the Inventory Function, I(z), for the Standard Normal Distribution Function \begin{tabular}{|c|c|c|c|c|c|} \hlinez & F(z) & I(z) & z & F(z) & I(z) \\ \hline-4.0 & .0000 & 0.0000 & 0.1 & .5398 & 0.4509 \\ \hline-3.9 & .0000 & 0.0000 & 0.2 & .5793 & 0.5069 \\ \hline-3.8 & .0001 & 0.0000 & 0.3 & .6179 & 0.5668 \\ \hline-3.7 & .0001 & 0.0000 & 0.4 & .6554 & 0.6304 \\ \hline-3.6 & .0002 & 0.0000 & 0.5 & .6915 & 0.6978 \\ \hline-3.5 & .0002 & 0.0001 & 0.6 & .7257 & 0.7687 \\ \hline-3.4 & .0003 & 0.0001 & 0.7 & .7580 & 0.8429 \\ \hline-3.3 & .0005 & 0.0001 & 0.8 & .7881 & 0.9202 \\ \hline-3.2 & .0007 & 0.0002 & 0.9 & .8159 & 1.0004 \\ \hline-3.1 & .0010 & 0.0003 & 1.0 & .8413 & 1.0833 \\ \hline-3.0 & .0013 & 0.0004 & 1.1 & .8643 & 1.1686 \\ \hline-2.9 & .0019 & 0.0005 & 1.2 & .8849 & 1.2561 \\ \hline-2.8 & .0026 & 0.0008 & 1.3 & .9032 & 1.3455 \\ \hline-2.7 & .0035 & 0.0011 & 1.4 & .9192 & 1.4367 \\ \hline-2.6 & .0047 & 0.0015 & 1.5 & .9332 & 1.5293 \\ \hline-2.5 & .0062 & 0.0020 & 1.6 & .9452 & 1.6232 \\ \hline-2.4 & .0082 & 0.0027 & 1.7 & .9554 & 1.7183 \\ \hline-2.3 & .0107 & 0.0037 & 1.8 & .9641 & 1.8143 \\ \hline-2.2 & .0139 & 0.0049 & 1.9 & .9713 & 1.9111 \\ \hline-2.1 & .0179 & 0.0065 & 2.0 & .9772 & 2.0085 \\ \hline-2.0 & .0228 & 0.0085 & 2.1 & .9821 & 2.1065 \\ \hline-1.9 & .0287 & 0.0111 & 2.2 & .9861 & 2.2049 \\ \hline-1.8 & .0359 & 0.0143 & 2.3 & .9893 & 2.3037 \\ \hline-1.7 & .0446 & 0.0183 & 2.4 & .9918 & 2.4027 \\ \hline-1.6 & .0548 & 0.0232 & 2.5 & .9938 & 2.5020 \\ \hline-1.5 & .0668 & 0.0293 & 2.6 & .9953 & 2.6015 \\ \hline-1.4 & .0808 & 0.0367 & 2.7 & .9965 & 2.7011 \\ \hline-1.3 & .0968 & 0.0455 & 2.8 & .9974 & 2.8008 \\ \hline-1.2 & .1151 & 0.0561 & 2.9 & .9981 & 2.9005 \\ \hline-1.1 & .1357 & 0.0686 & 3.0 & .9987 & 3.0004 \\ \hline-1.0 & .1587 & 0.0833 & 3.1 & .9990 & 3.1003 \\ \hline-0.9 & .1841 & 0.1004 & 3.2 & .9993 & 3.2002 \\ \hline-0.8 & .2119 & 0.1202 & 3.3 & .9995 & 3.3001 \\ \hline-0.7 & .2420 & 0.1429 & 3.4 & .9997 & 3.4001 \\ \hline-0.6 & .2743 & 0.1687 & 3.5 & .9998 & 3.5001 \\ \hline-0.5 & .3085 & 0.1978 & 3.6 & .9998 & 3.6000 \\ \hline-0.4 & .3446 & 0.2304 & 3.7 & .9999 & 3.7000 \\ \hline-0.3 & .3821 & 0.2668 & 3.8 & .9999 & 3.8000 \\ \hline-0.2 & .4207 & 0.3069 & 3.9 & 1.0000 & 3.9000 \\ \hline-0.1 & .4602 & 0.3509 & 4.0 & 1.0000 & 4.0000 \\ \hline 0.0 & .5000 & 0.3989 & & & \\ \hline \end{tabular}