A mass m$=1\mathrm{.}1$kgm$=1\mathrm{.}1$kg is at the end of a horizontal spring on a frictionless horizontal surface. The mass is oscillating with an amplitude A$=4\mathrm{.}5$cmA$=4\mathrm{.}5$cm and a frequency f$=1\mathrm{.}6$Hzf$=1\mathrm{.}6$Hz$.$

Write an equation for the spring constant kk in terms of the variables in the problem statement $($that is to say, only use the variables and do not concern yourself with the assigned values$).$

kk $=$