9000007210

Jane has to reach the opposite shore of a lake. She has three possibilities how to cross. She can use her own boat, start immediately and sail at the velocity $4\mathrm{km}/\mathrm{h}$. Another option is to wait for her friend, Peter, with a faster boat. Peter's boat is capable to sail at the velocity $10\mathrm{km}/\mathrm{h}$. However, his boat will be available in $1.5$ hours from now. The last option is to use the regular passenger transportation line which will departure in $2.25$ hours from now and sails at the speed $20\mathrm{km}/\mathrm{h}$. Find the interval of distances to the opposite shore for which the fastest option is to use Peter's boat.