-8.67× 10^6 N/C
The Electric Field is defined as force per unit charge.
E = Q/ 4π£r2
Qv= −6.5 μCm3
Qv = Q/ V= Q/ 4/3 πr3
Hence Q = 4/3 πr3 × Qv
Hence E = 4/3 πr3 × Qv / 4π£r2= Qvr/3£
−6.5 μ × 4/ 3×8.854 ×10^-12
-6.5 × 4 × 10^6/3 = -8.67× 10^6 N/C
Note: £ = 8.854×10^-12m/F
is the permittivity of free space
Qv is the charge per unit volume
V is volume and volume