Just sub in 7 wherever you see r in dA/dr
A sum of 1600 dollars is deposited in an account with an interest rate of r percent per year, compunded daily. At the end of 7 years, the balance in the account is given by
A=1600 (1 + r
36,500
)2555 .
dA/dr= 112 *(1+r/36,500)^2554
then If r = 7, then dA/dr= ??? dollars/(one percentage point).