A charge enters a region of the uniform magnetic field with a velocity and experiences a force …

A charge $10\ \mu\text{C}$ enters a region of the uniform magnetic field with a velocity $(4\hat{i} + 5\hat{j})\text{ m/s}$ and experiences a force $(5\hat{i} - C\hat{j})\text{ N}$. Find the value of 'C'.