Answer:
 He invest $10101.01.
Explanation:
Given : Mark knows that he will need to buy a new car in 5 years. The car will cost $15,000 by then. 
To find : How much should he invest now at 8%, compounded quarterly, so that he will have enough to buy a new car? 
Solution : 
Using compound interest formula, 
 
 
Where, A is the amount A=$15000
P is the principle P=? 
r is the rate r=8%=0.08
t is the time t= 5 years 
Substitute the value, 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Therefore, He invest $10101.01.