Question 1106913
T(t)  =  −7 + Ae^(−kt)
:
(a) t = 0
86 = -7 + A
A = 93
:
(b)  29 = -7 + 93 * e^(20k)
e^(20k) = 36/93 = 0.3871
20k = ln 0.3871 = −0.9491
k = −0.9491/20 = −0.0475
:
(c)  T(t) = -7 + 93 * e^(28*−0.0475) = 17.5964
after 28 minutes 17.5964 C
:
(d)  0 = -7 + 93 * e^(t*−0.0475)
 e^(t*−0.0475) = 7/93 = 0.0753
t*−0.0475 = ln 0.0753 = −2.5863
t = −2.5863/−0.0475 = 54.4484 minutes the drink will be 0C
: