Create Sharepoint 2013 List item using PowerShell and REST API

$url="http://server/sites/PaySllips/_api/lists/GetByTitle('Pay Slips')/items"
$url1="http://server/sites/PaySllips/_api/contextinfo"                    #to get request digest

#$credentials=Get-Credential



#getting request digest
$RequestDigest=Invoke-RestMethod -Uri $url1 -Method POST -UseDefaultCredentials
$RequestDigest=$RequestDigest.GetContextWebInformation.FormDigestValue


#getting ListItemEntityTypeFullName
$List = Invoke-RestMethod -uri $url -UseDefaultCredentials
$ListItemEntityTypeFullName = $list.entry.content.properties.ListItemEntityTypeFullName
$ListItemEntityTypeFullName



$body = "{ '__metadata': { 'type': '$ListItemEntityTypeFullName' }, 'Title': 'Hello'}"
$header = @{"accept" = "application/json;odata=verbose""X-RequestDigest" = $RequestDigest

}

Invoke-RestMethod -Method Post -Uri $url -Body $body -ContentType "application/json;odata=verbose" -Headers $header -UseDefaultCredentials

Above is the code i am trying to create List item using PowerShell and REST API.

But i get error 400 bad request on my last command  "Invoke-RestMethod -Method Post -Uri $url -Body $body -ContentType "application/json;odata=verbose" -Headers $header -UseDefaultCredentials"

Any suggestion about what i am doing wrong??