$dV =-\overrightarrow{ E } \cdot \overrightarrow{ dx }$

$\int_{T_{ r }}^{ V _{ R }} dV =-\int_{0.5}^2 \frac{2 k \lambda}{ x } dx$

$V _{ R }- V _{ P }=-2 k \lambda \ln \frac{2}{0.5}$

$=-2 \times 9 \times 10^9 \times 3 \times 10^{-9} \times 2 \times 0.7=-126$

due to sphere

$v_R-v_P=\frac{k Q}{2}-\frac{k Q}{1}=-\frac{k Q}{2}=\frac{-9 \times 10^9 \times 10 \times 10^{-9}}{2}$

$=-45 V$

$v_R-v_P=-126-45=-171 V$

$v_p-v_R=171 V$