Find how much should be invested to have 19,500 in 10 months at 7.5% simple interest

What is the multiplicative rate of change of the exponential function shown on the graph?

For the rule of 78, for a 12-month period, the last term in the sequence is 12 and the series sums to 78. for an 10 month period, the last term is and the series sum is . for a 15 month period, the last term is and the series sum is . for a 20 month period, the last term is and the series sum is

What are the first 4 terms in the multiplication pattern given by the formula 2×4n