Question

In an electrically heated home, the temperature of the ground in contact with a concrete basement wall is 13.9

Answer 1

Fourier's Law express conductive heat transfer as
q = k A dT / s (1)
where
A = heat transfer area (m2, ft2)
k = thermal conductivity of the material (W/m.K or W/m oC, Btu/(hr oF ft2/ft))
dT = temperature difference across the material (K or oC, oF)
s = material thickness (m, ft)

Assume K = 1.7 for concrete

q = (1.7 W/moC) x ( 8.7) x (19.7 - 13.9) / (0.12 m)

= 714.85 watts

1 dollar = 5 Kilowatt hours or 5000 watthours so

Time for 1 dollar = 5000/714.85 = 6,99 hours or 7 hours 39 minutes