A certain polymer can be modeled approximately by means of a Maxwell model with a modulus of elasticity of 15 MPa and a viscosity of 250 MPa-s. Starting from a neutral configuration, a sudden strain of 3% is applied and maintained for 10 seconds. At this point of time the applied strain is suddenly reduced to 2% and 10 seconds later increased to the original value. Find the value of the stress a further 10 seconds later, that is, exactly 30 seconds after the beginning of the loading process.