please answer question c and d

5. [18 marks] [Proper sentences are required] m A materials testing laboratory performed destructive testing on 1,000 solid Douglas-r beams and 1,000 engineered lumber composite (ELC) beams of the same dimensions. The average bending strength of the ELC beams was found to be lower than that of the Douglas-r beams. However, when all of the data from these tests were used by the appropriate grading organization, the allowable design stress derived for the ELC was higher than for the solid Douglas-r. [2] (a) Explain what is meant by the term \"engineered lumber composite\". [2] (b) What is an \"allowable design stress\"? [8] (c) Why was the allowable design stress calculated for the ELC higher than that calculated for solid Douglas-r? Draw an appropriate diagram that illustrates the concept (not the composition of the ELC). [6] ((1) Describe the composition of a named engineered luber composite and explain how that contributes to it having a higher allowable design stress than solid Douglas-r