a
\(\,\phi \,\, = \,\,EScos\theta \,\, = \,\,3\,\, \times \,\,1{0^3}\,\, \times \,\,{[10\,\, \times \,\,{10^{ - 2}}]^2}\,\, \times \,\,\cos {60^ \circ }\,\, = \,\,3\,\, \times \,\,{10^3}\,\, \times \,\,{10^{ - 2}}\,\, \times \,\,\frac{1}{2}\,\, = \,\,15\,\,N{m^2}/\,C\)