can I please have the solution for this question

the rise in prices during this period. 14. Table 3.13 shows the monthly index of sales of a good during the first four months of the year. Table 3.13 Month Jan Feb Mar Apr Index 100 120 145 150 (a) Which month is chosen as the base year? (b) If sales in February are 3840, what are the sales in April? (c) What is the index number in May if sales are 4256