[tex]f=(9.0\times{10}^{9}\frac{N.{m}^{2} }{ {c}^{2} })\frac{(3.2 \times{10}^{ - 9}c) \: (9.6 \times {10}^{ - 9}c) }{(0.32 m)^{2}} \\ \\ f=(9.0\times{10}^{9}\frac{N.{m}^{2} }{ {c}^{2} })\ \frac{ \: 30.72 \times {10}^{ - 18} \: {c}^{2} }{ \: 0.1024 \: {m}^{2} } \\ \\f = \frac{9.0 \times {10}^{9} \times 30.72 \times {10}^{ - 18} }{0.1024} \: ( \frac{N.{m}^{2} }{ {c}^{2} } \: \times \frac{ {c}^{2} }{ {m}^{2} } )\\ \\ f = \frac{276.48 \times {10}^{ - 9} }{0.1024} \: ( \frac{N.{m}^{2} }{ {c}^{2} } \: \times \frac{ {c}^{2} }{ {m}^{2} } )\\ \\ f = 2700 \times {10}^{ - 9} N \\ \\ f = 2.7 \times {10}^{ - 6} N[/tex]
I hope I helped you^_^
