Let R be the rectangle with vertices (0,0), (4,0), (4,4), and (0,4) and let f(x, y)=2xy−−−√. (a) Find reasonable upper and lower bounds for ∫RfdA without subdividing R.

Suppose you are choosing a 6-digit personal access code. this code is made up of 4 digits chosen from 1 to 9, followed by 2 letters chosen from a to z. any of these digits or letters can be repeated. find the total number of personal access codes that can be formed. 492,804 341,172 39,917,124 4,435,236