Thread: refresh rates ,resolution and blah

Consider a noninterlaced raster monitor with a resolution n*m(m scan lines and n pixels per scan line ) a refresh rate of r frames /second ,a horizontal retrace time of T(horiz) and a vertical retrace time of T(vert).What is the fraction of the total refresh time per frame spent in retrace of the electron beam


I tried

Total refresh time /frame=total T(horiz)/frame +total T(vert)/frame

total T(horiz)/frame=m*T(horiz) because it takes T(horiz) to scan 1 scan line /frame
T(vert)/frame is the same because it's given /frame I don't know how to make use of the 2 givens that we have n pixels /scan line and the r refresh rate ? can anyone help?