Solve the Investment Problem $\$ 5000$ Last Year from a Part-Time Job

Multiple Choice

Solve the investment problem.
-Walt made an extra $\$ 5000$ last year from a part-time job. He invested part of the money at $10 \%$ and the rest at $8 \%$ . He made a total of $\$ 420$ in interest. How much was invested at $8 \%$ ?

A) $\$ 1000$
B) $\$ 3000$
C) $\$ 4000$
D) $\$ 2500$