For part A you know that m equals 10t so you just sub it in. So it is at first A(m)=π(10t)2 . Which you simplify to A(m)= π20t. You can simplify futher by multiplying by pi. Then part B you use the same equation but sub in a 3 for the t. So it would be A(m)=π20(3) which should equal out to 188.4
