Please help me with these exercise! Thank you!

1.3) A certain radioactive isotope has a half-life of approximately 1250 years. How many years to the nearest year would be required for a given amount of this isotope to decay to 70% of the original amount? Hint: Set 0.5 = e 1250k and solve for k, which should be expressed to 7 decimal positions. Then use the value for k and 0.7 (instead of 0.5) to solve for t, the time required for decay to 70%. Round answer to nearest whole number of years. 1.4) Coffee is best enjoyed at a temperature of 124F. A restaurant owner wants to discover the temperature T at which he should serve his coffee so that it will have cooled to this ideal temperature in 3 minutes. He discovers that a cup of coffee served at 198F cools to 183F in one minute when his restaurant is at 74F. If he maintains the restaurant temperature at 74F, at what temperature should he serve the coffee to meet his goal? Hint: Use Newton's Law of Cooling. Make sure to use 1/60 lufor 1 minute and 1/20 hor 3 minutes 1.5) A lake is stocked with 584 sh of a new variety. The size of the lake, the availability of food, and the number of other sh restrict growth in the lake to a limiting value of 3650. The population of sh in the lake aer time t, in months, is given by the lnction P(t) = 3650 1 + 4.916 -0.29t. After how many months will the population be 3432? Hint: Substitute 3432 for P(t) and solve for t