#### Answer

0.1333, 0.5714

#### Work Step by Step

Without bolt-on trace elements:
c = 260, d = 290, 1/d-c = 1/30
$P(280 \leq x \leq 284) = 1/30. ∫_{280}^{284} dx$
= 1/30. (284-280)
= 0.1333
With bolt-on trace elements:
c = 278, d = 285, 1/d-c = 1/7
$P(280 \leq x \leq 284) = 1/7. ∫_{280}^{284} dx$
= 1/7. (284-280)
= 0.0.5714