Relative rate of growth question??

The problem says to use the formula P=P1e^(kt) to fill in the missing vales of k. And P=pop. in the later year, P1=pop. earlier in the year, k=relative growth rate of world pop. per year,t=number of years between the two successive date.The first value is shown k=.28 for 1650. That plus the table below is all the info it gives me.How do I find k for the other years???

Year World population in millions. Relative rate of growth(percent/year)

1650 550 .28

1750 725 k

1850 1175 k

1900 1600 k

1950 2556 k

1980 4458 k

1999 5996 k