Explanation to how we got 31

Budgeted sales are $35 in April, $30 in May, and $25 in June. You expect to collect 80% of a month's sales in the month of the sales and 20% in the following month. Compute expected cash receipts (inflows) for May. A. not enough information-depends on the mix of fixed and variable cash flows B. $29 C. $29 D. $31 E. $65