If the activity of a radioactive substance is initially 396 disintegrations/min and two days later it is 281 disintegrations/min, what is the activity four days later still, or six days after the start? Give your answer in disintegrations/min.

Four point charges each having charge q are located at the corners of a square having sides of length a. find symbolic expressions for the following. (a) the total electric potential at the center of the square due to the four charges (use any variable or symbol stated above along with the following as necessary: ke.) vtotal= (b) the work required to bring a fifth charge p from infinity to the center of the square (use any variable or symbol stated above along with the following as necessary: w=