Setting PWM frequency to 5khz + setting duty cycle in us

Hi, I need to write a sketch that can deliver a one us pwm pulse every 200us at 5khz.

Could someone please help with how to work out the maths for setting the frequency to 5khz please?
Also is there a library available to set duty cycle by us rather than percentage?
This is to be used on an arduino UNO R3.

Many thanks Chris

You can bit bang the desired pin to achieve the frequency you want but I'm not sure how you would set it to pulse for 1us every 200us. You cannot get a 5khz pulse in 1us as it takes 200ms for a 5khz pulse. What exactly are you trying to do?