Which equation is equivalent to the formula r=st?

What is the standard form of -5x^2+2x^4-11+x^3+3x

A. 127 cm^2 b. 144.5 cm^2 c. 172 cm^2 d. 50 cm^2

Ricky takes out a $31,800 student loan to pay his expenses while he is in college. after graduation, he will begin making payments of $190.66 per month for the next 30 years to pay off the loan. how much more will ricky end up paying for the loan than the original value of $31,800? ricky will end up paying $ more than he borrowed to pay off the loan.