The amount that will be in his account after 4 years can be calculated below
[tex]\begin{gathered} I=\frac{PRT}{100} \\ p=\text{ \$3000} \\ R=4.2\text{ \%} \\ T=4 \\ I=\frac{3000\times4.2\times4}{100} \\ I=\frac{50400}{100} \\ I=504 \end{gathered}[/tex]The amount that will be in his account after 4 years is $504 + 3000 = $3504