A city council plans to renew its fleet of 60 police patrol cars by retiring 4 every month and buying 5 new cars. how many months will it take to replace the entire fleet of police cars?
Choose the correct option.
A) 15	B) 16	C) 10	D) 18	E) 13
Total fleet--60   End of 1st month -- (retires 4 and buys 5) total fleet--61(56 old 5 new).   End of 2nd month -- (retires 4 and buys 5) total fleet--62(52 old 10 new).   End of 3rd month -- (retires 4 and buys 5) total fleet--63(48 old 15 new).   End of 4th month -- (retires 4 and buys 5) total fleet--64(44 old 20 new).   End of 5th month -- (retires 4 and buys 5) total fleet--65(40 old 25 new).   End of 6th month -- (retires 4 and buys 5) total fleet--66(36 old 30 new).   End of 7th month -- (retires 4 and buys 5) total fleet--67(32 old 35 new).   End of 8th month -- (retires 4 and buys 5) total fleet--68(28 old 40 new).   End of 9th month -- (retires 4 and buys 5) total fleet--69(24 old 45 new).   End of 10th month -- (retires 4 and buys 5) total fleet--70(20 old 50 new).   End of 11th month -- (retires 4 and buys 5) total fleet--71(16 old 55 new).   End of 12th month -- (retires 4 and buys 5) total fleet--72(12 old 60 new).   End of 13th month -- (retires 4 and buys 5) total fleet--73(8 old 65 new).   End of 14th month -- (retires 4 and buys 5) total fleet--74(4 old 70 new).   End of 15th month -- (retires 4 and buys 5) total fleet--75(0 old 75 new).   15nswer is 15--after 15 months the council has totally replaced its fleet .
<result>A</result>
A city council plans to renew its fleet of 60 police patrol cars by retiring 4 every month and buying 5 new cars. how many months will it take to replace the entire fleet of police cars?