Output torque of a geared DC motor at a given current

A brushed DC motor has a torque constant $K_t = 0.05\,\text{N·m/A}$ and is driven at a steady $4\,\text{A}$. It connects to the load through a gearbox with reduction ratio $20{:}1$ and an efficiency of $90\%$. Assuming steady-state operation, what is the torque delivered at the gearbox output (the load side), in N·m?