Answer
$U_1= 86 MeV $
Work Step by Step
$U_1 \approx U_2 (\frac{q_{Pb} q_C }{q_{Rn} q_{He}}) $
Where
$U_2 = 30 MeV$
$q_{Pb} = 82 e$
$q_C = 6.0e$
$q_{Rn} = 86 e$
$q_{He} = 2.0 e$
so
$U_1 = 30 MeV (\frac{(82 e) (6.0e) }{(86 e)(2.0 e)}) $
$U_1= 86 MeV $