7.12 A strip of elastomer 1 mm x 1 mm x 10 cm that obeys the affine network model is stretched to 40 cm length at T=300 K at the engineering stress 1 x 107 Pa. The volume occupied by each monomer is b = 80 . (i) What is the relative elongation X? (ii) Find the shear modulus G. (iii) How many moles of network strands are in this rubber strip? (iv) Estimate the number of monomers between crosslinks.