36.

(a) We use C = ε

0

A/d to solve for d:

d =

ε

0

A

C

=

8.85

× 10

−12 C

2

N

·m

2



(0.35 m

2

)

50

× 10

−12

F

= 6.2

× 10

−2

m .

(b) We use C

∝ κ. The new capacitance is C



= C(κ/κ

air

) = (50 pf)(5.6/1.0) = 280 pF.