I worked this about an two hours ago. Perhaps for another student.

Normally, the concn curves for spectrophotometric work is done by plotting A (absorbance) on the Y axis and c (concn) on the x axis.

Since you have a straight line, the equation for a straight line is

y = mx + b where m is the slope and b is the y intercept. Since the line passes through the origin, b=0 and the equation becomes y = mx

Changing to the way graphs are made, this beomes A = m*c. The slope in the problem (m) is 1550.2; therefore, the equation becomes

A=1550.2*c.

You have c, calculate A(bsorbance). For transmittance, remember that A = log (1/T) or if you want it in %T directly it is A = log (100/%T)