Wholemark is an Internet order business that sells one popular New Year's greeting card once a year. The cost of the paper on which the card is printed is $0.55 per card, and the cost of printing is $0.20 per card. The company receives $3.45 per card sold. Because the cards have the current year printed on them, unsold cards have no salvage value. Its customers are from the four areas: Los Angeles, Santa Monica, Hollywood, and Pasadena. Based on past data, the number of customers from each of the four regions is normally distributed with a mean of 6,000 and a standard deviation of 350. (Assume these four are independent.)

What is the optimal production quantity for the card?

Note: Use Excel's NORMSINV() function to find the correct critical value for the given -level. Do not round intermediate calculations. Round Normsinv value to 4 decimal places. Roundup your answer to the nearest whole number.