Doris has $20,000 to invest. Her financial planner recommends that she diversify into three investments:

Treasury bills that yield 5% simple interest,

Treasury bonds that yield 7% simple interest, and corporate bonds that yield 10% simple interest.

Doris also wishes to earn $1,390 per year in income.

Also, Doris wants her investment in Treasury bills to be $3,000 more than her investment in corporate bonds.

How much money should Doris place in each investment?