ANSWER:
a) 4 m/s^2
b) 520 N
STEP-BY-STEP EXPLANATION:
The centripetal acceleration can be calculated as follows:
[tex]\begin{gathered} a_c=\frac{v^2}{r} \\ \text{ replacing} \\ a_c=\frac{4^2}{4}=\frac{16}{4}=4m/s^2 \end{gathered}[/tex]And we calculate the centripetal force like this:
[tex]\begin{gathered} F_c=m\cdot a_c \\ \text{ Replacing} \\ F_c=130\cdot4 \\ F_c=520\text{ N} \end{gathered}[/tex]