Question

Getting a differential equation:
A chemical reaction proceeds in such a way that after the first second, the amount of a certain chemical involved in the reaction changes at a rate that's inversely proportional to the product of the mass of the chemical present (in grams) and the time elapsed since the reaction began (in seconds). The mass m=m(t) of this chemical is modeled with WHAT differential equation with t is greater than or equal to 1 second?