Law of sines and the law of cosines

Find dy/dx using implicit differentiation ln(20+e^xy)=y

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

The distribution of the amount of money spent by students for textbooks in a semester is approximately normal in shape with a mean of $235 and a standard deviation of $20. according to the standard deviation rule, how much did almost all (99.7%) of the students spend on textbooks in a semester?