The formula for the future value vv (in dollars) of an investment earning simple interest is v=p+prtv=p+prt, where pp (in dollars) is the principal, rr is the annual interest rate (in decimal form) and tt is the time (in years). a. solve the formula for p. p=[] b. an investment earns 8% simple interest. what amount of principal is needed to have $6000 after 7 years? round your answer to the nearest cent. amount of principal: $[] a. p=v/rt+1