Need help solving this problem:

jamal is planning to invest up to 24,000 in City Bank or State Bank. He wants to invest at least 3,000 in city bank, but not more than 11,000; since state bank does not insure more than $18,000, he wants to invest no more than this amount in state bank. The interest at city bank is 6%, and the interest at State bank is 11 %. How much should he invest in each bank to earn the most interest?



Answer :

$24,000 ---------> City or State Bank
$3,000 < City Bank < $11000
State Bank< $18,000
City Bank = .06 of interest
State Bank = .11 of interest

Bold= Answer

State Bank - (18, 000)(.11)-----> $1980
                                                          } Total Interest = $2,430
City Bank - (6000)(.06)---------->$ 360
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State Bank - (13000)(.11) ----------> $1,430
                                                             } Total Interest = $2,090
City Bank - (11000)(.06) -------------> $660
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State Bank- (17000)(.11) ---------->$ 1870
                                                               } Total Interest = $2,290
City Bank- (7000)(.06) ---------------->$ 420