Rondon said in the club statement: "It's an honour to be here and I'm excited to get started with my team-mates".
"The clubs were talking for a long time, and now I'm focused on the season to help my team-mates to get the points to do well this season.
I would like to perform well and leave my name in Newcastle's history", Muto added.
"Hopefully we will continue working hard together to ensure the team stay in the Premier League".More news: Gov. Scott treads the Trump effect carefully in Tampa
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Joining the club before their relegation from the Premier League in 2016, it is widely suspected that Benitez's future at the club is in jeopardy if Ashley adheres to this stringent approach.
As reported by Sportsmail over the weekend, manager Benitez had quickly grown frustrated over Newcastle's lack of activity in the market.
Benitez is adored by the Geordie Faithful, but has something of a strained relationship with the North East clubs controversial owner Mike Ashley, and only last week admitted that he was anxious that he has not signed more players this summer. The players have no problem with the media, but it's a way of letting people know they're unhappy. The Venezuelan striker has not scored more than ten goals in any of his three seasons at West Brom but s the type of striker who contributes elsewhere in attack and will facilitate other attackers coming into play. Can we do it? Yes. It's impossible because we have lost the opportunities.
"My obligation is to try to improve the squad as much as I can until the last day".
"So if you're taking that stand, you have to be very conscious of what you are doing, and what you are trying to do is publicly force the owner into spending more money".