Freight car loadings over an 18-week period at a busy port are as follows:

Week	Number	Week	Number	Week	Number
1	260	7	325	13	405
2	265	8	345	14	410
3	270	9	365	15	460
4	265	10	360	16	465
5	270	11	380	17	470
6	275	12	400	18	475

a. Determine a linear trend line for expected freight car loadings.

Y ˆ Y^ = + t

b. Use the above trend equation to predict expected loadings for Weeks 20 & 21.

The forecasted demand for Week 20 is and for Week 21 is .

c. The manager intends to install new equipment when the volume exceeds 840 loadings per week. Assuming the current trend continues, in which week (at the earliest) should the loading volume reach that level?