One of your friends from another school asks for your help with his problem in Riemann sum. He needs to answer his assignment but unfortunately, he left his module in school. He wants to know how to approximate the area under the curve. He sent the problem, and ask you favor to explain step by step on how to obtain the area in any endpoint you prefer (right, left or midpoint).

Here is the problem.

"If the given function is y = x+1, and the interval is [0, 4] and the chosen number of rectangles to be used is 4, the approximated areausing left method is ___."

Please give the complete solution with concepts involve in the solving. Thank you!