Please help with the following Physics questions

[2] 1. (a) State Kirchhoff's laws. ( b ) For the circuit shown in Fig. 1.1, determine the currents labeled 1, 12, and I3. [8] 10 52 15 02 10 52 12 V 3 Fig. 1.1 A 1.0 g sample of the radioactive isotope 43TC has a half-life of 360 min. (a) How many atoms are present in the 1.0 g sample? (b) What is the activity of the 1.0 g sample of this isotope? (c) How long will it take for the activity of the 1.0 g sample to decrease to 1/3 of its original value? [10] Data: Avogadro constant = 6.02 x 10- mol" An object positioned 30.0 em in front of a thin lens forms an image on a screen 10.0 cm behind the lens. (a) Find the focal length of the lens. (b) Determine the magnification of the lens. (c) Is the lens converging or diverging? (d) Draw a ray diagram to show how the image is formed. [10]