An investor has up to $450,000 to invest in two types of investment. Types A pays 6% annually and type B pays 10% annually. To have a well-balanced portfolio, the investor imposes the following conditions. At least one-half of the total portfolios is to be allocated to type A investments and at least one-fourth of the portfolio is to be allocated to type B investments. What is the optimal amount that should be invested in each type of investment? What is the optimal return?

my question is how to get the equations/constraints from this question? i can't really understand how to get it out...

please help me out.....thank you