How do I solve this with the dataset, Theoph in RStudio to figure out ka and co

The rate of change of the amount in the stomach is given by the following model:

dy1/dt = -kay1

where ka is a rate parameter in hr^-1, and the initial amount of theophylline is given by y1(0) = co in mg. In other words, co is the amount of theophylline that the person initially ingests.

Exercise: What is your value of ka? What is your value of co? Include units in your answer.