Differential Equation system Problem

Can anybody help? (Headbang)

A system is modelled by Tx' + x = Ky

given the following results deduce the parameters T and K

. When the input y(t) of 5 units was applied the output x(t) ultimately settled with a value of 20 units

. when a sinusoidal input was applied at an input frequency of 10 rad/s the output lagged behind the input by exactly -45 degrees.

ii) if y(t) was a step change drive, at what time would x(t) reach half of its final steady state value ( T & K deduced previously)