HELP ASAP PLEASE 12. A sample of water was taken from a distant water source and analyzed for lead and mercury. When a 100 gram sample of water was taken and analyzed, it was
determined to contain 0.0036 grams of lead and 0.00012 grams of mercury What are
the concentrations in parts per million (ppm)?

answer: semi-infinite solid initially at a uniform temperature of 400 ◦c is cooled at its surface by convection. the cooling fluid at a constant temperature of 200 ◦c has a convective coefficient (ha) of 250 w/m2.k. the physical properties of the solid: k = 20 w/m.k and α = 4 * 10-5  m2/s. using δx = 0.04 m and δt = 10 s. write the finite difference equations describing the transient heat transfer of the first five δx and the temperature profile after 30 s.