We often associate carbon emissions on the basis of population growth and energy consumption. use the following estimation of carbon emissions: carbon emissions (kg c/yr) = population × energy (kj/yr)/person × carbon (kg c)/energy (kj) using the following estimates for the united states and assuming growth rates remain constant: population (kj/yr)/person kg c/kj 1990 amount 250×106 320×106 15×10-6 growth (%/yr) 0.6 0.5 -0.3 a. find the carbon emission rate in 1990. b. find the carbon emission rate in 2018. c. find the total carbon emitted in those 28 years. (c kg)