U_xx = 1

bc: u=0 on both ends.

find u for n_interval = 4

how the error drops at each step of interval increament?

what's the order of accuracy of your numerical solution?

its c i just checked it

the total distance that martina travels that day is

(distance from home to mom's office) plus (distance from mom's office to school)

plus (distance from school to library) plus (distance from library to friend's house)

plus (distance from friend's house to martina's house).

(we don't know what any of these distance actually is.)

it is b. absorbs thermal energy

one "light year" is the distance that light travels, through vacuum, in one julian year.   that's 365.25 days, of 24 hours each.