Correct answer is letter B. sandstone
Answer:1200
Explanation:
Given data
Upper Temprature
Lower Temprature 
Engine power ouput
Efficiency of carnot cycle is given by





rounding off to two significant figures

The maximum speed is 10.4 m/s
Explanation:
For a body in uniform circular motion, the centripetal acceleration is given by:

where
v is the linear speed
r is the radius of the circular path
In this problem, we have the following data:
- The maximum centripetal acceleration must be

where
is the acceleration of gravity. Substituting,

- The radius of the turn is
r = 10 m
Therefore, we can re-arrange the equation to solve for v, to find the maximum speed the ride can go at:

Learn more about centripetal acceleration:
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GPE= height x mass x gravitational field strength
5 x 10 x 9,8=490J
Given that,
Energy 
Surface temperature = 11000 K
Emissivity e =1
(a). We need to calculate the radius of the star
Using formula of energy



Put the value into the formula


(b). Given that,
Radiates energy 
Temperature T = 10000 K
We need to calculate the radius of the star
Using formula of radius

Put the value into the formula


Hence, (a). The radius of the star is 
(b). The radius of the star is 