Assume that the rate of decay of a radioactive substance is proportional to the amount of the substance present. The half-life of a radioactive substance is the time it takes for one-half of the substance to disintegrate. Carbon dating is often used to determine the age of a fossil. For example, a humanoid skull was found in a cave in South Africa along with the remains of a campfire. Archaeologists believe the age of the skull to be the same age as the campfire. It is determined that only 2% of the original amount of carbon-14 remains in the burnt wood of the campfire. Complete parts (a) through (e) below. a. Estimate the age of the skull ifthe half-life of carbon-14 is about 5720 years. b. Estimate the age of the skull if the half-life of carbon-14 is about 5620 years. The skull is about years old.