$1400 is divided between two accounts. One account pays $3%$ interest, while the other pays $4%$. At the end of the interest period, the interest earned was $50. How much was invested in each account?

Aresearch study is done to find the average age of all u.s. factory workers. the researchers asked every factory worker in ohio what their birth year is. this research is an example of a census survey convenience sample simple random sample