how do i solve these?

"A Practice Final - MA 121, section 0 X Course Hero X *Course Hero X X C webassign.net/web/Student/Assignment-Responses/submit?dep=24330742&tags=autosave#question289444_11 18. [-/2 Points] DETAILS The cost of a first-class postage stamp in 1962 was 4%. In 1999 it is 330. The cost was (and is) growing exponentially. What was the growth rate? NOTE: Pay attention to the symbol next to the answer blank. What will be the cost of a first-class postage stamp in 2010? 19. [-/1 Points] DETAILS Find the area under the curve y = 7x - x2 from x = 0 to x = 7 20. [-/1 Points] DETAILS Find the area of the region bounded by the two curves: y = x2 +4 y = 4x + 4 21. [-/2 Points] DETAILS Solve the separable differential equation for y: dy Note: Use "c" as an arbitrary constant. Answer in the form: y = Ae(xB + c) B = Type here to search O w 199 7:32 PM 11/17/2020