I am struggling with physics 5C due to having a horrible physics professor who is hard to understand and read his handwriting. Although I've tried studying via Khan Academy, I am still struggling immensely with homework problems. I'm hoping someone can help walk me through step by step how to solve problems 4.1, 4.2, and 4.3. This would be immensely appreciated, thank you !

Problem 4.1 Find the magnitude and direction of the four unknown currents. 1A 3A 2A 4 A Problem 4.2 A copper wire is connected across a battery's terminals. Current flows through the wire so that the power provided by the battery is Py. After stretching out the copper wire uniformly, tripling its length, what is the power P; provided by the battery? Problem 4.3 A thermistor is a special type of ohmic resistor whose resistance varies strongly with temperature. In a typical application, a small' current I, is passed through the thermistor while precisely measuring the potential drop V across the thermistor. If the thermistor's temperature- dependence has been characterized as R = R,eP/T-1/To) where Ry, 8, and Tj are known through calibration, find the thermistor's temperature 7