Issue 1574

[zmcNotafraid]

What problem does this PR solve?

When exchange_rate returns an integer, it will caused error.So we need to transfer it to decimal.

Check List

Test

• unit test

  Task

  • none

[coveralls]

Pull Request Test Coverage Report for Build fe4f7982e793002e21bd50857839940bd0b7c69e-PR-1577

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.03%) to 55.101%

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Totals
Change from base Build 6ea5d0c473764ee1b76309f655275fee851fd5d1:	0.03%
Covered Lines:	3327
Relevant Lines:	6038

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💛 - Coveralls