Verified answer

For it to slide with a constant velocity means that the forces along the ramp must sum to zero.

Along the ramp you have friction (acting up)

Force of you F (acting Up)

Component of weight (m*g*sin(theta)) acting down.

Perpendicular to the ramp You have the Normal and component of weight (m*g*cos(theta))

So N= m*g*cos(theta)

The frictional force Ff = mu*N = mu*m*g*cos(theta)

So F + mu*m*g*cos(theta) - m*g*sin(theta) = 0 If F is + then we were pushing up if its negative we were pushing down

So F = m*g*(sin(theta) - mu*cos(theta)) = 324*(sin(21) - .326*cos(21)) = 17.5N

Up the ramp