A parallel plate capacitor is formed by two plates each of area 30$\pi$ cm² separated by 1 mm. A material of dielectric strength 3.6 $\times$ 10⁷ Vm^$-$1 is filled between the plates. If the maximum charge that can be stored on the capacitor without causing any dielectric breakdown is 7 $\times$ 10^$-$6C, the value of dielectric constant of the material is :

[Use ${1 \over {4\pi {\varepsilon _0}}} = 9 \times {10^9}$ Nm² C^$-$2]