$2-)$

a$)$ If we let $R_x(t)=ln{M}_x(t),$ show that $R_x^{\text{'}}(0)=$ and $R_x^{\text{'}\text{'}}(0)={}^2$

b$)$ If $M_x(t)=e^{4(e^t-1)}$ find $$ and ${}^2.$