I've tried working this problem with a couple different formulas, but I still can figure out how to do it:

An upright meter stick 53.8m away is viewed through an inverting telescope with a 5x eyepiece. The observed image subtends an angle of 0.151 radians. What is the angular magnification of the telescope? What is the focal length of the objective lens?

For angular mag I've tried using m=d/fo, but I don't know fo, the focal point. I'm pretty confused on this.