I found the order (first order) but I don't see how I can calculate the value of the rate constant without a rate! I only have time and M(right column). How do I calculate it? I know k= (A) and I haven't a clue on how to predict the concentration at 280 s. Will someone explain to me please?

The data below show the concentration of versus time for the following reaction:

Time M

0 1.000

25 0.822

50 0.677

75 0.557

100 0.458

125 0.377

150 0 .310

175 0.255

200 0.210

Determine the value of the rate constant: ???

Predict the concentration of at 280: ?????