$2-20.$ Find the thermal resistance values of the following materials:

a$)8"$ thick lightweight concrete block

b$)\frac{3}{8^{\text{'}\text{'}}}$ thick plywood

c$)"$ actual thickness$)$ softwood lumber

d$)\frac{3}{4^{\text{'}\text{'}}}$ fiberglass insulation board

e$)\frac{5}{8^{\text{'}\text{'}}}$ thick gypsum wallboard

f$)$ Asphalt shingles thick$)$

g$){12}^{\text{'}\text{'}}$ thick cellulose insulation blown into an attic space