(a) put in t = 3 into the r(t) equation provided. Answer will be in gigameters
(b) Use the value of r(t) found in part (a) in the surface area of a sphere equation. S = 4(pi)r² Answer, S will be in units Gm²
(c) This is saying put the equation r(t) into the equation S(r) to make a new equation S(t) or h(t) as they put it.
h(t) = 4(pi)(1.36t + 0.002)²
(d) Put t = 3 into the new equation. Answer will agree with b