8. What is the surface area of the given figure? (1 point) 26 cm
10 cm
34 cm
mm
24 cm
drawing not to scale

Ifound your complete question in other sources.  see attached image.  part a:   the equation modeling the problem is an exponential equation of the form:   y = a (b) * ^ t  where,  a: initial amount  b: decrease rate  t: time  substituting values we have:   y = 1000 (0.80) ^ t  part b:   for this case we substitute the value of y = 640 in the equation:   640 = 1000 (0.80) ^ t  we cleared t:   640/1000 = (0.80) ^ t  log0.80 ((0.80) ^ t) = log0.80 (640/1000)  t = log0.80 (640/1000)  t = 2 years