Compute the gross income, gross taxable income, annual income tax, and net income $($less tax$)$ given the following problems using the two income tax schedules, prior to $2018$ and after $2018.$

Mr$.$ Kiel is an employee working for Ms$.$ Cruz, his employer. He is the head of the family with $3$ qualified dependents. Mr$.$ Kiel earns a monthly salary equivalent to

P$40,000.$

Mr$.$ Corona is a single dad with $2$ children and works as a Vice president of a food corporation. Mr$.$ Corona earns P$120,000\mathrm{.}00$ per month.